Bi-component polyacrylonitrile filaments and process for producing the same



United States Patent Int. Cl. n01r 7/02 US. Cl. 161-175 6 Claims ABSTRACT OF THE DISCLOSURE A method of conjugate spinning a bi-component fiber consisting of a homopolymer of acrylonitrile and a copolymer of acrylontrile containing at most 20 weight percent of a copolymerizable hydrazido betaine.

This invention relates to bi-component textile fibres from acrylonitrile polymers and to a method for the production of bi-component fibres having a reversible crimp and advantageous dyeing properties.

It is already known that two suitable spinning solutions or melts can be spun using suitable apparatus to form two-component filaments in which the two components lie adjacent one another in the cross-section of the filaments. It is also known that filaments of this kind can develop a permanent, three-dimensional crimp providing the two components are shrinkable to different extents. In addition, it is known that two-component filaments can be produced from acrylonitrile polymers, the crimp of which is three-dimensional and varies under the influence of a swelling agent, for example water, returning to its original condition following removal of the swelling agent. A crimp of this kind is known as a reversible crimp. Reversibility is obtained by virtue of the fact that the two components which lie adjacent one another in the filament diifer in their capacity to absorb swelling agents, in particular water. The difference in their hydrophilic properties can be brought about by a difference in the ionisable group content. In addition, it has already been proposed to use acrylonitrile copolymers with sulphobetaines to produce two-component fibres with a reversible crimp.

The reversible-crimp bi-component fibres produced from acrylonitrile polymers usually contain a polymeric component with a large number of ionisable groups of acid or basic character, strongly acid groups such as sulpho groups, for example, being preferred. Where dyeing is carried out with basic dyes for example the hydrogen or alkali metal ions in the sulpho groups of the polymer are exchanged for the donor cation of the dye. All the hydrogen or alkali metal ions are exchanged for dye ions providing firstly that a sufliciently long dyeing time is used and, secondly, that sufficient dye is used.

In the case of reversible-crimp bi-component fibres containing strongly acid groups, the saturation value and dye absorption rate is unusually high on account of the large number of dye-receptive groups. As a result, it is extremely diflicult for the dyes to be evenly applied. This is particularly the case where the object of dyeing is to produce bright shades. The addition of retarding agents eliminates only some of these difficulties.

In conventional reversible-crimp bi-component fibres, a polymer with an extremely low number of ionisable groups is present in the fibre in addition to a polymer with a large number of ionisable groups. For this reason, the saturation value and absorption rate of the two fibre components vary quite considerably. The appearance of such fibres after dyeing is aesthetically unsatisfactory because the dye does not have any brightening power. For this reason, it has already been proposed to add another polymer with dye-receptive groups to the polymer containing an extremely small number of ionisable groups, and to use this mixture as one of the components of the filament. Unfortunately, this method is somewhat complicated and can only obviate some of the disadvantages which occur. Another disadvantage of bi-component fibres in which one of the components contains strongly ionised groups, is the fact that, after dyeing, their reversibility decreases because the hydrophilic groups are saturated with dye ions.

It has also been proposed to use copolymers of acrylonitrile and sulphobetaines as one of the component fila ments in the production of reversible-crimp fibres. The sulphobetaines used as comonomers are neutral and do not have any afiinity for dyes. For this reason, it is either impossible or takes an excessively long time to dye fibres containing polymers of this kind as one of their components dark or deep shades. In addition, filaments produced from such polymers are hydrophilic to a limited extent only and hence only show a limited reversibility of crimp, particularly when they are exposed to the high temperatures, normally used in the production of fibres. In addition, the polymers, for example vinylpyridine-sulphobetaine, show a marked tendency to go yellow.

It is an object of this invention to provide bi-component fibres consisting of a homopolymer of acrylonitrile and a copolymer of acrylonitrile containing at least 70% by weight of acrylonitrile in combination with other polymerizable unsaturated compounds, using at most 20% by weight of a copolymerizable hydrazido betaine of the formula and A represents an aliphatic, aromatic or araliphatic radical having an unsaturated copolymerizable group, R is an alkylene radical and R and R" represent C to C alkyl radicals which together with the nitrogen atom may form a heterocyclic ring system.

A further object of this invention is a method of producing bi-component fibres having a reversible-crimp and which do not suffer from the aforementioned disadvantages as regards dyeing by spinning together a polymer of acrylonitrile as the first component, and, as the second component, a copolymer of acrylonitrile and copolymerisable, unsaturated hydrazido betaines compounds corresponding to the following general formula RI x- -nn-z r a-soswherein X is A or ANH or .A-NH-C H and A represents an aliphatic aromatic ,or araliphatic radical with an unsaturated copolymerisable group, R represents an alkylene radical, R and R" represent lower alkyl radicals or, together with N, represent a heterocyclic radical, stretching the resulting bi-component filament and heat-setting the filaments, fibres or the formed woven 3 or knitted fabrics. The heatsetting may be effected at temperatures of between 70 C. to about 150 C.

The following compounds of this kind are mentioned by way of example:

(a) Unsaturated copolymerisable oarboxylic acid bydrazide sulphobetaines (X=A) (c) Unsaturated copolymerisable oxalamidohydrazidesulphobetaines (X A-NH-CO):

These compounds can be prepared by quaterm'sing the corresponding unsaturated carboxylic acid hydrazides, semicarbazides or oxalamidohydrazides with cyclic sulphonic acid esters such as propane sultone or butane sultone.

Compounds with these structures have the ability to assume different degrees of dissociation in the acid range at difierent pH-values of a bath, for example the dye bath. Since only the dissociated groups are available for dye absorption, it is possible in the case of fibres containing polymers with these compounds as comonomers, to adjust the saturation value and absorption rate as required by the pH-value of the dye bath. In this way, it is possible to obtain optimum conditions for brightor dark-shade dyeing by suitable adjusting the pH-value. It is also possible in this way ideally to assimilate the dyeing properties of the two components, thus eliminating any disadvantages arising out of the difference in dyeability of the two components. In addition, suitable aftertreatment leaves two component fibres produced with these comonomers as one of the components, with a threedimensional reversible crimp in the sense that the crimp changes under the action of a swelling agent, for example water and returns to its original condition follownig removal of the swelling agent. This also applies as regards dyed two-component fibres of this kind.

The polymers may contain between 1 and 20%, preferably between 5 and 10%, of the aforementioned comonomers. Copolymerisation can be carried out by known processes using radical-forming catalysts, preferably with the persulphate/bisulphite Redox system in aqueous medium. Additionally, other copolymerisable unsaturated compounds may be combined with the hydrazido betaine monomers, such as acrylic acid esters, methacrylic acid esters and vinyl compounds. The relative viscosity of the co-polymers [1 1, as measured at 20 C. in dimethyl formamide at a concentration of 0.5 g./ ml., can with advantage be between 1.7 and 2.7.

Clear, bright and eminently spinnable solutions can be produced from the copolymers, whilst the spun filaments are white and exhibit outstanding thermal stability. The other polymer used in the preparation of the twocomponent filaments is with advantage a homopolymer of acrylonitrile. It can be prepared by known processes, for example by precipitation polymerisation in aqueous medium using Redox catalyst systems. In place of a homopolymer, it is also possible to use a copolymer of acrylonitrile with 1 to of comonomer which does not contain any ionisable groups such as, for example, methyl acrylate, methyl methacrylate or vinyl acetate. The relative viscosity a of these polymers can with advantage be between 1.7 and 2.7.

To prepare the two-component filaments, the two polymers are dissolved separately. Suitable solvents include the solvents normally used for polyacrylonitrile, for example dimethyl formamide, dimethyl acetamide or dimethyl sulphoxide. The two solutions are spun together by the conventional processes used to produce two-component filaments.

With two-component filaments, relaxation of the filaments or fibres in boiling water, followed by drying, results in the development of a permanent crimp when the two components, which lie beside one another in the fibre, dilfer in the extents to which they shrink. The crimp thus developed is reversible when the component with the greater shrinkage can also be swollen to a greater extent than the component with the lower shrinkage. In this case, the tensions between the components which originally resulted in crimping, can be eliminated to some extent when the crimped fibres are treated with swelling agent, so that when wet the fibres show fewer crimping curls or bends. Following removal of the swelling agent and drying, the crimp returns to its original condition. One'method of testing the components, after they have been combined to form a two-component filament, for their ability to develop a crimp following suitable after treatment, is to measure the extent to which filaments which were subjected to the same after-treatment as single-component filaments, shrink on boiling. A difference in the shrinkage on boiling shows that a twocomponent filament made up of the two components is able to develop a crimp following suitable after treatment. One method of testing the components for their ability to develop a reversible crimp after they have been combined to form a two-component filament, is to measure the longitudinal swelling of the single-component filaments. A difference in longitudinal swelling of approximately 0.4% or more between the two single component filaments indicates that the crimp of the two-component fibres will become reversible. Finally, the reversibility of the two-component fibres can be directly measured.

In order to measure the extent to which a single-component fibre shrinks on boiling, the length of a fibre or of a small group or band of fibres is measured with a cathetometer under a small load (0.2 g./l80 den.). The fibre or the band of fibres is then boiled in water for 30 minutes free from any strain, dried at 70 C. over a drying agent and its length re-measured. The shrinkage on boiling is calculated from the initial length I and the final length in percent, as

100 (ZAZE)% ZA To measure the longitudinal swelling of a single component fibre, a fully shrunk fibre or a band of fully shrunk fibres is treated entirely free from strain for a period of 5 hours in water heated to 70 C. The length of the specimen thus treated is measured with a cathetometer. The specimen is then dried in vacuo over P 0 without any strain. The specimen is then kept for one hour over P 0 in a cathetometer vessel under a load of 0.2 g./ 180 den. Its length is then re-measured by means of a cathetometer. The wet-dry cycle is repeated until reproducible values are obtained. The reversible longitudinal swelling in percent is calculated from the length L of the swollen fibre and the length L of the de-swollen, dry fibre, as

(LA LE) LE To determine the reversibility of a two-component fibre, a fibre is secured between two grips and boiled free from strain in water, dried for 24 hours at 70 C. and then cooled to room temperature. The number of crimping curls in the fibre when it is dry (K is then determined by counting. The fibre held free from strain between the two grips is then kept for 6 hours in water heated to 70 C. in a separate vessel and the number of crimping curls in the fibre thus swollen (K The dry-wet cycle is repeated until reproducible values are obtained. The reversibility of crimp is calculated in percent as 100 (KT-Kg) KT EXAMPLE 1 A copolymer of acrylonitrile containing 5% by weight of a carboxylic acid hydrazide sulphobetaine corresponding to the formula with an 1 value of 2.17, is converted with dimethyl formamide into a 23% by weight solution and spun by a conventional dry spinning process into single-component filaments with an individual denier of 9.6 (filaments A). A homopolymer of acrylonitrile with an 1 value of 2.17 is converted with dimethyl formamide into a 23% solution and spun by the same method into single component filaments with an individual denier of 9.6 (filaments B). The filaments are each stretched in a ratio of 1:4 in water heated to 98 C. and then wound on to a bobbin. Some of the filaments are dried for one hour at 70 C. under tension, and the other heated under tension for 15 minutes at C. The shrinkage on boiling and reversible longitudinal swelling of the filaments is then measured:

Shrinkage onlzaoiling, Reversible longitudinal Two stretched bands or ribbons, one consisting of filaments A and the other of filaments B, are each dried in a rotary dryer at 130 C., crimped in a compression crimper chopped into staple fibres and treated with steam at 116 C. The fibres are dyed for one by a standard process in a boiling dye bath at different pH-values. The dye bath contains 8% of Astrazonblau B (Colour Index, 2nd edit., vol. III, No. 42140). The liquor ratio is 1:40. The pH values 2 and 2.5 are adjusted with H SO and the others with acetic acid or acetic acid/Na-acetate. The pH-dependent dye-absorption of filaments A is clearly apparent. In the case of filaments B, there is no evidence at all of pH-dependent dye absorption.

The dyed and dried filaments A are dissolved in dimethyl formamide to which 1% cone. sulphuric acid has been added (25 mg. of fibres in 200 ml.) and the extinction values of the dyed solutions measured at 625 m Extinction of filaments A 7 EXAMPLE 2 The solutions of Example 1 are spun by a conventional dry-spinning process into two-component filaments with an individual denier of 9.6. The filaments are stretched in water heated to 98 C. in a ratio of 1:4, and then airdried in a drying zone heated to 130 C. The filaments are then compression crimped and chopped into fibres. A sample of the fibres is boiled for 30 minutes in water and the reversibility of the crimp measured. It amounts to 38.0%.

EXAMPLE 3 A copolymer of acrylonitrile containing 8% of a carboxylic acid hydrazide sulphobetaine corresponding to the with an 1;,,; value of 2.63, is made up into a 22% solution with dimethyl formamide and spun by a conventional dryspinning process into single-component filaments with an individual denier of 9.6. The filaments are stretched in water heated to 98 C. in a ratio of 1:4, dried under tension at 130 C. in a rotary dryer, crimped in a compression crimper, chopped into staple fibres and treated with steam at 116 C. One sample of each fibre is dyed at different pH-values by the standard process of Example 1. The pH-dependent dye absorption is clearly apparent. The extinction values of the dyed and dried fibres are measured as in Example 1:

pH-value: Extinction 2.0 0.36 2.5 0.57 3.0 0.71

EXAMPLE 4 EXAMPLE 5 A copolymer of 90% of acrylonitrile and of a semicarbazide sulphobetaine corresponding to the formula [1;, =2.17] is converted with dimethyl formamide into a 25% solution and, together with a 23% solution of a homopolymer of acrylonitrile with an 1 of 2.17, is spun by a conventional process into two-component filaments with an individual denier of 9.6. The filaments are stretched in water heated to 98 C. in a ratio of 1:4, shrunk by 20% in a drying zone heated to 130 C. and then dried. The filaments are compression crimped and chopped into staple fibres. A sample is boiled for 30 minutes in water and the reversiblllty of 1ts crunp measured.

It amounts to 39%.

EXAMPLE 6 A copolymer of acrylonitrile containing 5% by weight of acrylic acid methylester and 8% by weight of an oxalic acid amide hydrazido betaine of the formula having a relative viscosity 1 of 1.93 was dissolved to a 27.5% by weight solution in dimethyl-formamide. The spinning procedure, the stretching and drying being carried out according to Example 1. Reversible longitudinal swelling: 6.6% (70 C.), 5.2% (130 C.). The same procedure was carried out with a 27% by weight solution of the copolymer and a 23% by weight solution of the acrylonitrile homopolymer. Reversibility of crimp: 46%.

EXAMPLE 7 A 22% by weight solution of an acrylonitrile homopolymer (1 =2.21) in dimethylformamide was spun together according to Example 1 with a 28% by weight solution of copolymer (1 =1.88) from by weight of acrylonitrile, 4% by weight of acrylic acid methyl ester and 6% by weight of the comonomer of the formula Reversibility of crimp: 41%. The procedure was repeated with the above mentioned copolymer but without the acrylic acid methylester component. The copolymer (94% acrylonitrile and 6% hydrazido betaine) has a relative viscosity 11ml. of 2.04. Reversibility of crimp: 35%.

What we claim is:

1. A bi-component fibre consisting of a homopolymer of acrylonitrile and a copolymer of acrylonitrile containing at least 70% by weight of acrylonitrile in combination with other polymerisable unsaturated compounds, using at most 20% by weight of a copolymerisable hydrazido betaine of the formula and A represents an aliphatic, aromatic or araliphatic radical having an unsaturated copolymerisable group, R is an alkylene radical and R and R" represent C to C -alky1 radicals which together with the nitrogen atom may form a heterocyclic ring system.

2. The bi-component fibre of claim 1, wherein said unsaturated copolymerisable group is the methacrylic acid group.

3. The bi-component fibre of claim 1, wherein said copolymer of acrylonitrile has a relative viscosity nreL of between 1.7 and 2.7.

4. A method for producing a bi-component fibre based on acrylonitrile polymers, which comprises spinning in conjugated form a homopolymer of acrylonitrile with a copolymer of acrylonitrile, containing at least 70% by weight of acrylonitrile, and other copolymerisable compounds using at most 20% by weight of a copolymerisable hydrazidobetaine compound the formula:

and A represents an aliphatic, aromatic or araliphatic radical with an unsaturated copolymerisable group, R represents an alkylene radical and R and R" represent lower alkyl radicals which, together with the nitrogen atom, may also form a heterocycle, stretching the resulting bi-component filament, and heat-setting the filament, the staplefibre or the Woven or knitted fabric.

5. The method of claim 4, wherein stretching being carried out in ratio of 1:4 at a temperature of about 100 C.

6. The method of claim 4, wherein said heat-setting being effected in a temperature range of between about 70 and about 150 C.

No references cited.

JULIUS FROME, Primary Examiner J. H. WOO, Assistant Examiner 

